ESQL: Generate kibana inline docs (#106782)

This takes a stab at generating the markdown files that Kibana uses for
its inline help. It doesn't include all of the examples because the
`@Example` annotation is not filled in - we're tracking that in
#104247 (comment)

There are some links in the output and they are in markdown syntax. We
should figure out how to make them work for kibana.

docs/reference/esql/functions/README.md

@@ -5,6 +5,8 @@ The files in these subdirectories are generated by ESQL's test suite:
 * `signature` - railroad diagram of the syntax to invoke each function
 * `types` - a table of each combination of support type for each parameter. These are generated from tests.
 * `layout` - a fully generated description for each function
+* `kibana/definition` - function definitions for kibana's ESQL editor
+* `kibana/docs` - the inline docs for kibana
 
 Most functions can use the generated docs generated in the `layout` directory.
 If we need something more custom for the function we can make a file in this

docs/reference/esql/functions/kibana/definition/abs.json

@@ -0,0 +1,60 @@
+{
+  "comment" : "This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.",
+  "type" : "eval",
+  "name" : "abs",
+  "description" : "Returns the absolute value.",
+  "signatures" : [
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "double",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "integer",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "integer"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "long",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "long"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "unsigned_long",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "unsigned_long"
+    }
+  ],
+  "examples" : [
+    "ROW number = -1.0 \n| EVAL abs_number = ABS(number)",
+    "FROM employees\n| KEEP first_name, last_name, height\n| EVAL abs_height = ABS(0.0 - height)"
+  ]
+}

docs/reference/esql/functions/kibana/definition/acos.json

@@ -0,0 +1,59 @@
+{
+  "comment" : "This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.",
+  "type" : "eval",
+  "name" : "acos",
+  "description" : "Returns the arccosine of `n` as an angle, expressed in radians.",
+  "signatures" : [
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "double",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "integer",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "long",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "unsigned_long",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    }
+  ],
+  "examples" : [
+    "ROW a=.9\n| EVAL acos=ACOS(a)"
+  ]
+}

docs/reference/esql/functions/kibana/definition/asin.json

@@ -0,0 +1,59 @@
+{
+  "comment" : "This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.",
+  "type" : "eval",
+  "name" : "asin",
+  "description" : "Returns the arcsine of the input\nnumeric expression as an angle, expressed in radians.",
+  "signatures" : [
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "double",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "integer",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "long",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "unsigned_long",
+          "optional" : false,
+          "description" : "Number between -1 and 1. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    }
+  ],
+  "examples" : [
+    "ROW a=.9\n| EVAL asin=ASIN(a)"
+  ]
+}

docs/reference/esql/functions/kibana/definition/atan.json

@@ -0,0 +1,59 @@
+{
+  "comment" : "This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.",
+  "type" : "eval",
+  "name" : "atan",
+  "description" : "Returns the arctangent of the input\nnumeric expression as an angle, expressed in radians.",
+  "signatures" : [
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "double",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "integer",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "long",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "number",
+          "type" : "unsigned_long",
+          "optional" : false,
+          "description" : "Numeric expression. If `null`, the function returns `null`."
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    }
+  ],
+  "examples" : [
+    "ROW a=12.9\n| EVAL atan=ATAN(a)"
+  ]
+}